1. Field of the Invention
The present invention relates to a liquid ejection apparatus and a recording apparatus, and more particularly, to a liquid ejection apparatus in which pressure variation caused by the pulsating flow by a pump can be suppressed while maintaining the liquid refill volume and the responsiveness of pressure adjustment.
2. Description of the Related Art
Conventionally, in a liquid ejection apparatus, a negative pressure is applied to the liquid inside the nozzles, in order to prevent the liquid from leaking out from the nozzles when ejection is not being carried out. In order to apply such a negative pressure, a negative pressure generating chamber is provided, in an ink cartridge, an ink tank or a sub tank which is connected to the nozzles, in order to generate a negative pressure by adjusting the pressure through supplying and evacuating air by means of a pump. However, pumps generally have a pulsating action, and there is a possibility that pressure variation may occur due to the effects of this pulsating action during pressure adjustment.
Therefore, Japanese Patent Application Publication No. 2004-106310 discloses a proposal for avoiding pressure variation caused by the pulsating action of a pump. As shown in FIG. 19 and FIG. 20, in Japanese Patent Application Publication No. 2004-106310, a pressure variation suppressor 204 comprising a filter 205 of a porous body is disposed between the ink supply apparatus 202 and the recording head 203. The vibration occurring during the supply of ink is suppressed, thereby preventing the pressure variation occurring in the ink supply apparatus 202 from being transmitted to the recording head 203.
Firstly, the principles of the generation of a pulsating action by the pump will be described with reference to a rotary pump. As shown in FIG. 21, in a rotary pump, a rotating body 211 rotates and compresses an elastic tube 212 which is held by a guide 213, thereby causing the air inside the elastic tube 212 to move and creating an outflow and inflow of air.
FIG. 22 is an expanded diagram of the guide 213 and the elastic tube 212 shown in FIG. 21. As shown in FIG. 22, when the rotating body 211 moves in the order of A, B, C and D (i.e. A→B→C→D) illustrated in FIG. 21, the volume of the region α in the elastic tube 212 which is positioned in the direction of movement of the rotating body 211 is reduced and the pressure increases accordingly as the rotating body 211 advances in the order of A, B, C and D (i.e. A→B→C→D). When the rotating body 211 passes D and then reaches the subsequent position, A′, as shown in the illustration indicated by (d) in FIG. 22, the rotating body 211 returns to the position of A, as shown in the illustration indicated by (a) in FIG. 22. In this case, the pressure in the elastic tube 212 affects the raised pressure at A′ and after, and hence there is a decline in the pressure at and after A′.
Therefore, the relationship between the position (phase) of the rotating body 211 and the pressure value at the part that is subject to the air supply by the rotary pump is as represented in FIG. 23. As shown in FIG. 23, as the position (phase) of the rotating body 211 advances in the order of A, B, C and D (i.e. A→B→C→D), the pressure value at the part subject to the supply increases at a constant ratio, but when the position (phase) of the rotating body 211 passes D and returns again to A, then the value of the pressure at the part subject to the supply falls temporarily. The breadth of this temporary decrease in the pressure value at the part subject to the supply affects a pulsating action in the air supply operation performed by the rotary pump.
Here, if the volume of the elastic tube 212 from A→B→C→D→A′ is taken to be v, and the volume from A′ is taken to be V, then the breadth of the pulsating action is expressed by N×v2/{V×(V+v)}, in other words, it is proportional to v2 and inversely proportional to V2. N is the number of repetitions. In order to make the apparatus compact in size, in particular, it is necessary to set the volume V of the part subject to the supply to a small volume, and in order to adapt to a large volume supply, it is necessary to set the volume v of the pump tube to a large volume. Therefore, the pulsating action becomes large and the pressure variation during pressure adjustment becomes large. Therefore, it is difficult to achieve the supply having a stable pressure. This is not limited to a rotary pump, and may also occur in the case of a piston type pump.
In the invention described in Japanese Patent Application Publication No. 2004-106310, the pressure variation caused by the pulsating action of the pump is suppressed by the porous filter as described above, but there is a possibility that the flow channel resistance is high, the response with respect to pressure adjustment is poor, and shortfall in the supply of liquid to the recording head may occur.